Barry Commoner, a founder of modern ecology and one of its most provocative thinkers and mobilizers, died Sunday in Manhattan. He was 95.

Commoner was a leader among a generation of scientist-activists who recognized the toxic consequences of America's post-World War II technology boom, and was one of the first to stir the national debate over the public's right to comprehend the risks and make decisions about them.

Raised in Brooklyn during the Depression and trained as a biologist at Columbia and Harvard, he came armed with a combination of scientific expertise and leftist zeal. His work on the global effects of radioactive fallout, which included documenting concentrations of strontium 90 in the baby teeth of thousands of children, contributed materially to the adoption of the Nuclear Test Ban Treaty of 1963.

From there it was a natural progression to a range of environmental and social issues that kept him happily in the limelight as a speaker and an author through the 1960s and '70s, and led to a wobbly run for president in 1980.

In 1970, the year of the first Earth Day, Time magazine put Commoner on its cover and called him the Paul Revere of ecology. He was by no means the only one sounding alarms -- the movement was well under way by then, building on the effect of Rachel Carson's book "Silent Spring" in 1962 and the work of many others. But he was arguably the most peripatetic in his efforts to make environmentalism a people's political cause.

Commoner was an imposing professorial figure, with a strong face, heavy eyeglasses, black eyebrows and a thick head of hair that gradually turned pure white. He was much in demand as a speaker and a debater, especially on college campuses, where he helped supply a generation of activists with a framework that made the science of ecology accessible.

His four informal rules of ecology were catchy enough to print on a T-shirt and take to the street: Everything Is Connected to Everything Else. Everything Must Go Somewhere. Nature Knows Best. There Is No Such Thing as a Free Lunch.

Having been grounded, as an undergraduate, in Marxist theory, he saw his main target as capitalist "systems of production" in industry, agriculture, energy and transportation that emphasized profits and technological progress with little regard for consequences: greenhouse gases, nonbiodegradable materials and synthetic fertilizers and toxic wastes that leached into the water supply. He insisted that the future of the planet depended on industry's learning not to make messes in the first place, rather than on trying to clean them up.

In a "Last Word" interview with the New York Times in 2006, Commoner elaborated on his holistic views and lamented the inability of society to connect the dots among its multitude of challenges, "an unfortunate feature of political development in this country."